Brake sticking.

After changing my front wheel it seems my front brake needs to be setup again. As far as i can tell the stock curvy calipars have two pistons on one side which keep pushing in until they meet something at which point they retract as the lever is released whilst there is a static pad on one side which the disc is clamped against?

Assuming that is correct it seems my static pad is too far out now. Discs, wheel and axle have all been checked and are straight (discs have say 3-5mm of movement side to side between them). The the gap between disc and static pad is about 5-6mm on each disc/brake.

So that i don't do it wrong is there a guide or any little things i should specifically not do?

Basically what do i do to adjust this static pad?

Cheers guys with your help im nearly back on the road!

[Paul the 6th]

as far as I remember, the calipers on the sv650's are sliding calipers. If you pump the brake lever a few times it should push the moving piston & pad against the disc, and in the process, pull the caliper tight up against the disc so that the 'static' pad and the whole caliper is sat correctly?

I'm a complete numpty though so just hang fire and see if anyone comes along to correct this.

Also, make sure both calipers are fitted and on the disc when you do this - if you have one caliper hanging free, the piston will be pumped out and it's a right slag to get them apart again

^ thats right but the slide might be stuck, so remove the calliper than pull both rubber boots back (the ones at attached the bolt hole bracket to the calliper ) and pull off the bracket stick a far amount off grease in the boots slide back in the right way and reattach if the problem persists it might be the pistons need cleaning a greasing, and/or the brakes need bleeding

[Sid Squid]

The sliders are sticking. Remove the caliper and remove the mounting , one goes into a hole in the caliper with a rubber right through, commonly there is corrosion on the outside of this rubber which causes the rubber to grip the pin. The other pin rarely sticks, but making everything slide neatly gives the best braking and improves the lever action. Clean everything and use rubber grease to lubricate the relevant parts.

Aha! I see it now, clever system makes all the avid, magura and hope braking systems i have been using for years on trials bikes seem bloody silly. My particular brake is mostly shades of grey-ey black. So even a clean would help! It does slide by hand just not a very smooth motion I'll have a good go at it once I get some grease.

Cheers guys.

Originally Posted by Elltg

Aha! I see it now, clever system makes all the avid, magura and hope braking systems i have been using for years on trials bikes seem bloody silly. My particular brake is mostly shades of grey-ey black. So even a clean would help! It does slide by hand just not a very smooth motion I'll have a good go at it once I get some grease.

Cheers guys.

why does it make them seem silly my hope m4's are better designed than the sv brake's, 2 pistons on one side 2 on the other more pistons usualy means more power

why do you think most SS bikes have 4 or 6 piston calipers and not sliding ones

[Sid Squid]

It doesn't matter how many pistons there are - there's only a difference if the total surface area of the pistons is different - the same area is the same force, independant of how many pistons it's spread across. There is of course the rigidity of the system to consider - opposed piston systems are fixed rather than sliding, (like single sided ones - SV brakes for instance), which means they are more rigid which further means that more of the total force is applied in clamping the brake pads rather than distorting the system.
But it's the same force per area, no matter how many pistons there are.

More pistons, appropriately arranged of course, allows a greater swept area from a given radius disc. Which can mean a narrower and lighter disc. Discs are unsprung weight, so that's good then.

so take my Hope m4's they have 4 pistons to small 2 large (1 of each per side) the callipers are a solid one pice construction and do not slide would they be more powerfull than a caliper that slides with one small and one large (diameter) piston ?

Originally Posted by Sid Squid

It doesn't matter how many pistons there are - there's only a difference if the total surface area of the pistons is different - the same area is the same force, independant of how many pistons it's spread across. There is of course the rigidity of the system to consider - opposed piston systems are fixed rather than sliding, (like single sided ones - SV brakes for instance), which means they are more rigid which further means that more of the total force is applied in clamping the brake pads rather than distorting the system.
But it's the same force per area, no matter how many pistons there are.

More pistons, appropriately arranged of course, allows a greater swept area from a given radius disc. Which can mean a narrower and lighter disc. Discs are unsprung weight, so that's good then.

.

[Sid Squid]

Originally Posted by barwel1992

so take my Hope m4's they have 4 pistons to small 2 large (1 of each per side) the callipers are a solid one pice construction and do not slide would they be more powerfull than a caliper that slides with one small and one large (diameter) piston ?

Depends. Clearly an opposed piston caliper can be rigidly mounted, any sliding caliper system will not be as rigid, In principle the opposed piston caliper has the potential to be more rigidly mounted and thus a less flexy system.
Note; less flexy, not inflexible - basic engineering principle: if a bending force is applied, bending occurs. That's not in question, the only question is how much bending?
But, when you say more power, no, if the total area of the pistons, (however many there are), is the same, and the other parts of the brake system are the same too, then there's always the same amount of 'power', ie force produced per given amount of line pressure. How well that force is transmitted into making the pads squeeze the disc is the deciding factor - how much flex is there in the system overall? There are some poor opposed piston calipers, and plenty of well designed and made sliding calipers, so whilst the rigidly mounted system should be better, the vagaries of design and manufacture are at least as important.
Your bike's brakes four pistons are different diameters for a specific reason. Put your hands together as if you were praying with your elbows about a foot apart, imagine your hands are the brake pads and between them is a disc going upwards, now keeping the angle between your hands and arms the same, bring your elbows together - the heels of your hands stay together and your fingertips spread apart. That's what happens to the pads as they grip the disc: their leading edges are pressed together by the disc dragging between them and the trailing edges are pulled apart leading to a greater braking force at one end of the pad than at the other. The different size pistons distribute the clamping force on the pads in different amounts as an attempt to even up the force across the whole of the pad.